Cylinder 1 Misfire Detected
What it means
The engine computer has detected repeated incomplete combustion in cylinder 1, based on crankshaft speed fluctuations during that cylinder's power stroke. Because the problem is limited to one cylinder, the cause is usually a part specific to it, such as its spark plug, ignition coil or injector.
Related lights
Dashboard lights that may come on with this code.
Symptoms4
- Steady engine shake at idle, felt in the steering wheel or seat.
- Loss of power, especially when accelerating or climbing hills.
- Check engine light on, possibly flashing when the misfire is severe.
- Higher fuel consumption and a smell of unburned fuel from the exhaust.
Possible causes6
- Worn, fouled or wide-gapped spark plug in cylinder 1.
- Weak ignition coil for cylinder 1 or a cracked coil boot, or a damaged plug wire on systems that use wires.
- Clogged or leaking cylinder 1 injector.
- Damaged wiring or connector at the cylinder 1 coil or injector.
- Vacuum leak at the intake manifold gasket near cylinder 1.
- Low compression from a leaking valve, worn rings or a failed head gasket (less common).
How to diagnose5
- Watch the cylinder 1 misfire counter on a scan tool and check whether other cylinders are also affected.
- Remove the cylinder 1 spark plug and check it for wear, color, oil or deposits.
- Swap the cylinder 1 coil with a neighboring cylinder, clear the codes and drive; if the other cylinder's code appears, the coil is at fault.
- If the misfire stays on cylinder 1, repeat the swap with the spark plug, then check the injector by listening for its click or with an injector balance test.
- Have a compression and leak-down test done if ignition and injector check out.
How to fix6
- Replace the spark plug, ideally all plugs if they are near their service interval.
- Replace the ignition coil if the misfire followed it in the swap test.
- Repair damaged wiring or connectors.
- Clean or replace the cylinder 1 injector if it is proven faulty.
- Repair the cause of low compression if the test confirms it.
- Clear the codes, then road test and confirm the code does not return.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
In the Saudi market: SAR 150–1,500 (≈ USD 40–400)
Our prices come from the Saudi market, converted at a fixed rate (SAR 3.75 per USD). Prices in your country may differ a lot, so we show the cost level.
The cost is low when a spark plug or coil is to blame, rises when a new injector is needed, and can go beyond this range if low compression requires internal engine repair.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026
Frequently asked questions
Can I drive with code P0301?
Only a short distance and gently until it is fixed. If the check engine light is flashing, stop, because unburned fuel from this cylinder overheats the catalytic converter and can destroy it.
How do I tell whether it is the coil or the plug?
Use a swap test: move the cylinder 1 coil to a neighboring cylinder; if the code changes to that cylinder, such as P0302, the coil is bad. If not, repeat the test with the plug.
Why did P0171 appear with P0301?
Cylinder 1 is always on bank 1, so a lean code on the same bank points to a vacuum leak near that cylinder or a weak injector feeding it.
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